Control device for use in metal working machines



July 18, 1961 A. s. CHARLAT 2,992,571

CONTROL DEVICE FOR USE IN METAL. WORKING IMCI-IINES Filed June 25, 1959 2 Sheets-Sheet 1 FIG. I

ATTORNEYS July 18, 1961 A. s. CHARLAT 2,992,571

CONTROL DEVICE FOR USE IN METAL WORKING MACHINES 2 Sheets-Sheet 2 Filed June 25, 1959 v ATTORNEY 3 United States Patent 2,992,571 CONTROL DEVICE FOR USE IN METAL WORKING MACHINES Arnold S. 'Charl'at, Norwalk, Conn., assignor, by mesne assignments, to Brown & Sharpe Manufacturing Company, Providence, 12.1., a corporation of Rhode Island Filed June 25, 1959, Ser. No. 822,953 Claims. (Cl. 7732.5)

This invention relates to machines for performing operations on workpieces by means of tools and having cooperating tool-holding and workpiecesupporting members, which are relatively movable toward and away from each other to present the tool to and retract it from the workpiece and one of which is rotatable to cause the operation to be performed. More particularly, the invention is concerned with a novel control device adapted for use in machines of the stated type and operative upon completion of a predetermined relative movement of the members to actuate a mechanism for stopping such movement or to give an indication to an operator, who then stops the movement. The new device may be used in machines of various types but, since all of the advantages of the device are realized when it is employed in machines for performing drilling, boring, and similar operations automatically, a drilling machine, in which a form of the device is incorporated, will be illustrated and described for purposes of explanation.

In drilling machines, in which the main spindle driving the tool rotates in a quill movable toward and away from the workpiece, it is common to employ a depth control mechanism including a stop element movable with the quill and engageable with an abutment, which is adjustable for drilling holes varying in depth. In automatic machines, in which the quill is moved by power, the engagement of the stop element with the abutment causes reversal of the means for moving the quill and, as a result, the tool is immediately retracted and the bottom of the hole drilled is left rough and unfinished. The proper finishing of the bottom of the hole requires that, when the tool reaches the bottom of the hole, it rotate a number of times without substantial advance into the workpiece but the depth control mechanisms now in use are not constructed to permit such rotation of the tool at the bottom of the hole for finishing purposes.

The present invention is, accordingly, directed to the provision of a control device for use in machines of the type above described, which, when used on automatic machines, functions after a predetermined relative movement of the workpiece-supporting and tool-holding members of the machine to stop such movement after a slight addition- 211 movement, during which the bottom of the hole is finished. When the device is used on a manually controlled machine, it indicates the extent of the additional relative movement of the machine members and thus provides the operator with information, which he must have in order to control the machine properly. In some instances, the device may both stop the tool feeding movement in an automatic machine and also indicate the extent of. the additional movement necessary for finishing purposes.

In its essentials, the device comprises a primary resilient element capable of being distorted under substantial pressure and a secondary resilient element mounted on the primary element. The primary element is engageable by the moving member of the machine, when a predetermined movement of the member corresponding to the drilling of a hole of a selected depth has occurred, and, as the member continues to move, the primary element is subjected to pressure causing it to be distorted. Such distortion ofthe primary element caused by a small movement of the member produces a bowing of the secice ondary resilient element and the movement of the middle of the secondary element is a multiple of the movement of the member applying distorting pressure to the primary resilient element and is utilized to reverse the means moving the member, to indicate such movement of the member, or to produce both effects. When the device is used on a drilling machine, the drilling continues during the slight additional movement of the member applying pressure to the primary element and the action of the tool at the bottom of the hole in the workpiece without substantial advance of the tool finishes the bottom of the hole and eliminates roughness.

For a better understanding of the invention, reference may be made to the accompanying drawings in which:

FIG. 1 is a view in front elevation, with parts removed, of a part of a drilling machine equipped with the device of the invention;

FIGS. 2 and 3 are sectional views on the lines 2-2 and 3-3, respectively, of FIG. 1;

FIG. 4 is a vertical sectional view through the device subjected to pressure; and

FIG. 5 is a diagrammatic plan view showing the application of the device to a lathe.

In the drawings, the device is shown in use with a drilling machine of the construction shown in my Patent 2,887,695, issued May 26, 1959. The machine of the patent includes a quill 10, in which is mounted the main driving spindle of the machine, and, at its. lower end, the quill carries a turret containing a plurality of tool holders which can be brought successively into operative relation to the spindle. The machine is provided with a depth control mechanism including a gear 11, in the hub of which are seated the lower ends of a plurality of threaded rods 12 carrying adjustably mounted washers 13 serving as abutment members. The rods correspond in number and position to the tool holders in the turret and, when the turret is adjusted to bring a particular tool holder into efiective relation to the spindle, the corresponding rod of the depth control mechanism is brought into effective relation to a lug on the quill.

The gear 11 rests upon the upper ring 141 of a thrust bearing and the lower ring 15 of the bearing rests upon a plurality of springs 16 seated at the bottom of a cup 17, which extends up into an opening in the lower face of the hub of the gear and is seated in a recess in the casing 18 of the machine. When the quill descends in the drilling of a hole in the workpiece, the lug on the quill engages the abutment member 13 in etfective position when a hole of a depth determined by the adjustment of the abutment member has been drilled. If the downward movement of the quill continues, the engagement of the lug on the quill with the effective abutment member causes gear 1 1 of the thrust bearing to be moved down against the resistance of the springs 16.

The casing of the machine is provided with a chamber 19 closed by a front closure plate 20 and lying below the cup 17. A primary resilient element in the form of a metal block 21 is mounted within the chamber 20 to rest upon a seat 22 and it is held in place by screws 23, 24 passing through openings in the block and into the rear wall of the chamber, the opening through the block for the screw 24 being slightly greater than the screw. The block has a central opening 25 extending through it and the opening is wider at the middle than at the ends so that, at its midpoint, the block is made up of two relatively thin spaced sections 26. Above and below the opening 25, the block is provided with transverse shoulders 27 and the ends of a secondary resilient element 28 having the form of a thin strip of metal and slightly longer than the normal distance between the shoulders 27 are seated against the shoulders. In order to place 3 the strip in position, it is slightly bowed and the engagement of its ends with the shoulders maintains it in that condition.

A pin 29 rests on the top of the block 21 and extends up through a passage in the casing 18 and through an opening in the bottom of the cup 17 to terminate in contact with the bottom race of the thrust bearing. Accordingly, when the lug on the quill engages the effective abutment member .13 and tends to move the gear 11 downward, such movement applies pressure through the thrust bearing and pin 29 to the top of the block 21. Because of the formation of the block with the two thin sections extending in the direction of the application of pressure and separated by the slot, the sections of the block are capable of being distorted under such pressure and such distortion of the block shortens the distance between the shoulders 27 and, as a result, the bowing of the secondary resilient element 2.8 is increased. The lateral movement of the middle of the secondary element thus produced is a multiple of the shortening of the length of the block under pressure and it is possible to design a block and a secondary element such that a decrease of .001" in the length of the block under pressure causes a lateral movement of the middle of the secondary element 28 of from .025 to .030". The lateral movement of the secondary element is utilized as follows.

A microswitch 38 is mounted on a bracket 31 secured to the rear face of the chamber 19 and the switch has an operating arm 32 lying in contact with the outer face of the secondary element 28 near its middle. The switch is in circuit with the means for moving the quill and, when the secondary element is bowed outward sufficiently by pressure applied to the block, the switch is actuated and reverses the moving means. As soon as the quill rises, the block and the secondary element resume their normal conditions and are in readiness for the next drilling operation.

When the device is used with a manually controlled machine, a conventional indicator 33 is mounted in an opening in the closure plate and held in place by a hollow stem 34 which extends from the back of the indicator and is clamped in an arm 35 attached to a plate 36 secured to the rear wall of the chamber 19. The actuating plunger 37 of the indicator extends through the stem 34 and lies in contact with the resilient element 28. When the secondary element is bowed outwardly by pressure causing distortion of the block 21, the plunger is moved endwise and causes the needle of the indicator to produce a corresponding indication. By watching the indicator, the operator can tell when he should stop the movement of the tool into the workpiece and the device thus contributes to the control of the machine. If desired, the device may be used, as shown in the drawings, both to actuate a switch and to. give an indication.

The application of the new device to a machine other than a drilling machine is shown in FIG. 5, in which the' device 38 is mounted on the bed 39 of a lathe in position to be actuated by a projection 44) on the tool carriage'41. As the carriage moves to the left during the operation of the machine, the projection ultimately engages the block 42 of the device and continued movement of the carriage causes distortion of the block and the outward bowing of a resilient element. Such movement of the element actuates an indicator 43, which shows the extent of additional movement of the carriage after the projection has engaged the block of the device and gives the operator information as to the proper time to stop the carriage movements.

I claim:

1. A device for use in a machine for performing operations on workpieces and having relatively movable tool-holding and workpiece-supporting members, which comprises a primary resilient element distortable under pressure, means operable by the moving member of the machine to apply pressure to the primary element sulficient to distort it, a secondary resilient element mounted on the primary element in bowed condition and subjected to increased bowing as the primary element is compressed, and control means actuated by movement of the bowed portion of the secondary element.

2. The device of claim 1, in which the primary resilient element is a metal block and means engaged by the moving member apply pressure to the end of the block.

3. The device of claim 2, in which the block has an opening through it separating narrow lengthwise sections distortable under pressure applied to the end of the block.

4. The device of claim 2, in which the block is provided with a pair of spaced opposed transverse shoulders and the secondary resilient element has its ends seated on the shoulders and is bowed outwardly away from the block.

5. The device of claim 1, in which the control means has an actuating member engaging the bowed middle part of the secondary resilient element.

6. The device of claim 1, in which the control means include a switch.

7. The device of claim 1, in which the control means include an indicator.

8. The device of claim 1, in which the secondary resilient element is a thin narrow metal strip.

9. A drilling machine, which comprises a quill movable toward and away from a workpiece to be operated on, a primary resilient element distortable under substantial pressure, means operable by the quill moving toward the workpiece to apply pressure to the primary resilient element suflicient to distort it, a secondary resilient element mounted on the primary element in bowed condition and subjected to increased bowing as the primary element is compressed, and means for controlling the movement of the quill actuated by movement of the bowed portion of the secondary element.

10. The drilling machine of claim 9, in which the primary resilient element is a metal block, to the end of which pressure is applied by the means operable by the quill, and the secondary resilient element is a thin narrow metal strip.

References Cited in the file of this patent UNITED STATES PATENTS 1,454,777 Walker May 8, 1923 2,208,635 Johnson July 23, 1940 2,442,949 Fischer June 8, 1948 FOREIGN PATENTS 367,789 Italy Feb. 2, 1939 

